Rewriting nuclear epigenetic scripts in mitochondrial diseases as a strategy for heteroplasmy control

Area of Science:

• Epigenetics
• Mitochondrial Biology
• Genetics

Background:

• Mitochondrial diseases stem from nuclear or mitochondrial DNA (mtDNA) mutations, with limited treatments.
• Reducing mutant mtDNA levels (heteroplasmy shift) is a key therapeutic strategy but faces challenges.
• Severe mitochondrial dysfunction induces nuclear epigenetic responses, specifically DNA methylation changes.

Purpose of the Study:

• To investigate if targeting nuclear DNA methylation can selectively impair cells with high mutant mtDNA loads.
• To explore the role of nuclear DNA methylation in regulating heteroplasmic cell survival.
• To assess DNA methylation inhibitors as a therapeutic strategy for mitochondrial diseases.

Main Methods:

• Utilized cybrid models with specific mtDNA mutations (m.13513 G>A and m.8344 A>G) at varying heteroplasmy levels.
• Analyzed nuclear DNA methylome alterations in response to different mtDNA mutation loads.
• Treated cells and xenografts with FDA-approved DNA methylation inhibitors.

Main Results:

• mtDNA mutation type and load significantly influence the nuclear DNA methylome.
• Specific DNA methylation patterns are crucial for the survival of cells with high heteroplasmy.
• DNA methylation inhibitors selectively reduced heteroplasmy in high-heteroplasmy cells.

Conclusions:

• Nuclear DNA methylation is a critical regulator of heteroplasmic cell survival.
• Targeting nuclear DNA methylation presents a promising therapeutic avenue for mitochondrial diseases.
• This approach offers a way to reduce heteroplasmy by selectively impacting cells with high mutant mtDNA loads.